When a seller offers you a partial refund, you have 10 days to accept or refuse it. If you don’t do anything, the offer will expire after 10 days.
The source of your original payment determines how you get the money back. If you paid for an item with a credit card, the refund will most likely go back to your credit card account or may be put into your PayPal balance. The same applies to your PayPal account or bank account.